Vascular catheter having low-profile distal end

ABSTRACT

An ultrasonic imaging catheter comprises a catheter body having a distal region and proximal region. The distal region has a reduced cross-sectional area compared to that of the proximal region, and the proximal region includes at least two lumens therethrough for accommodating a movable guidewire and a rotatable working element, respectively. The catheter body may be inserted over the movable guidewire, with the guidewire passing through a lumen in the distal region and the guidewire lumen in the proximal region. After positioning the catheter body, the guidewire can be retracted from the distal region and into the proximal region, leaving the lumen in the distal region available for the rotatable working element. Such a construction allows over-the-wire imaging of the catheter while minimizing the width of the catheter in the dital region which remains available for placement of the working element.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present application is a continuation of U.S. applicationSer. No. 09/351,800, filed on Jul. 13, 1999, which is a continuation ofU.S. application Ser. No. 07/975,769, filed on Nov. 13, 1992, now U.S.Pat. No. 5,997,523, which is a continuation-in-part of U.S. applicationSer. No. 07/930,977, filed on Aug. 14, 1992, now U.S. Pat. No.5,203,338, which is a continuation of U.S. application Ser. No.07/629,500, filed on Dec. 17, 1990, now abandoned. The priority of theseprior applications is expressly claimed and their disclosure are herebyincorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates generally to the construction anduse of vascular catheters and, more particularly, to vascular cathetershaving a reduced-size distal tip capable of selectively receiving eithera movable guidewire or a work element.

[0004] Arteriosclerosis, also known as atherosclerosis, is a commonhuman ailment arising from the deposition of fatty-like substances,referred to as atheroma or plaque, on the walls of blood vessels. Suchdeposits occur both in peripheral blood vessels that feed limbs of thebody and coronary blood vessels that feed the heart. When depositsaccumulate in localized regions of the blood vessels, blood flow isrestricted and the person's health is at serious risk.

[0005] Numerous approaches for reducing and removing such vasculardeposits have been proposed, including balloon angioplasty, where aballoon-tipped catheter is used to dilitate a stenosed region within theblood vessel; atherectomy, where a blade or other cutting element isused to sever and remove the stenotic material; and laser angioplasty,where laser energy is used to ablate at least a portion of the stenoticmaterial; and the like.

[0006] In order to more effectively apply such interventionaltechniques, a variety of vascular imaging devices and methods employed.Of particular interest to the present invention, intraluminal imagingcatheters having ultrasonic transducers at their distal ends have beenemployed to produce images of the stenotic region from within the bloodvessel.

[0007] A number of particular designs for such ultrasonic imagingcatheters have been proposed. One approach has been to use a phasedarray of discrete ultrasonic imaging transducers at the tip of avascular catheter. While such an approach is advantageous in that itdoes not acquire mechanical manipulation of the transducers, it isproblematic in that the image quality is limited. Such phased arrayintravascular imaging catheters are commercially available fromEndoSonics Corporation, Rancho Cordova, Calif., as the CathScanner ISystem.

[0008] A more promising approach for intravascular ultrasonic,imagingemploys mechanical rotation of the ultrasonic signal, either bymechanically rotating the transducer itself or by mechanically rotatinga mirror which radially deflects the ultrasonic signal from thetransducer. Such mechanical rotation generally provides a better imagequality than use of a phased array system, but the design of thecatheters is problematic since the designs must provide for rotating thetransducer and/or an associated mirror at speeds usually in the rangefrom 500 to 2000 rpm. Moreover, the interior blood vessel must beprotected from the rotating components which could cause substantialinjury should they come in contact with the blood vessel.

[0009] A number of specific designs for mechanical ultrasonic imagingcatheters have been described. An early design is illustrated in U.S.Pat. No. 4,794,931, where the mechanical components of the imagingsystem are located within a housing at the distal end of the catheter.The housing includes a fixed guidewire at its distal tip that is used toposition the catheter within the vascular system. While the use of suchfixed-guidewire designs can provide an excellent image quality, undersome circumstances it is desirable to use an “over-the-wire” designwhere the catheter may be introduced over a separate (movable)guidewire. The use of a movable guidewire has certain advantagesincluding improvement in steering capability through branch coronaryarteries and elsewhere and facilitating catheter exchange, e.g.,substitution of an interventional catheter after the imaging has beencompleted.

[0010] A particular design for an over-the-wire ultrasonic imagingcatheter is illustrated in FIG. 1. The catheter includes the catheterbody 10 having an exterior catheter lumen 12 attached near its distalend. A rotatable ultrasonic imaging assembly 14 is mounted at the distalend of the drive member 16, and the device may be introduced over aconventional movable guidewire is, as illustrated. Such designsemploying parallel lumens, however, are disadvantageous since the widthof the distal tip in the region of the ultrasonic imaging element mustbe sufficient to also accommodate the guidewire. Ideally, to be able tocross very narrow lesions, the diameter of the catheter in the region ofthe imaging element should be minimized, preferably including only theimaging element to be rotated and a catheter sheath surrounding theimaging element. The requirement of the separate guidewire lumenincreases this minimum size, making the design unsuitable for smallblood vessel type lesions and for passing through conventional guidingcatheters.

[0011] Designs of the type illustrated in FIG. 1 are commerciallyavailable from Medi-Tech, Inc., Watertown, Mass. A design similar tothat of FIG. 1 is illustrated in co-pending application Ser. No.07/422,935, the disclosure of which is incorporated herein by reference.

[0012] An alternative design for a mechanical ultrasonic imagingcatheter avoids the requirement for a parallel guidewire lumen byproviding for exchange of the mechanical imaging components with aconventional guidewire. As illustrated in FIG. 2, such a cathetercomprises a single lumen catheter sheath 20 that can receive a drivewire 22 carrying an ultrasonic imaging assembly 24 at its distal end.The catheter sheath 20 may be initially introduced over a conventionalguidewire. The guidewire may then be completely removed and replacedwith the imaging assembly. While the diameter of the catheter 20 may beminimized, the need to exchange the guidewire and imaging componentswhenever the catheter is to be repositioned is time consuming anddisadvantageous. Such catheters are commercially available fromInter-Therapy, Inc., Costa Mesa, California, (now Cardiovascular ImagingSystems, Inc., Sunnyvale, Calif., assignee of the present application).

[0013] For these reasons, it would be desirable to provide ultrasonicimaging catheters which combine a narrow profile in the region of theultrasonic imaging components and an ability to be introduced over aseparate, moveable guidewire. It would be particularly desirable if suchdesigns would allow for imaging within the narrow distal region of thecatheter without the need to remove the guidewire from the catheterbody. In particular, such imaging catheter should present a width ofless than about 5 French, and more preferably being less than about 3French, to facilitate entry into the coronary arteries and even verytight lesions.

SUMMARY OF THE INVENTION

[0014] According to the present invention, vascular catheters comprise acatheter body having a proximal end and a distal end. The catheter bodyincludes at least a distal region extending proximally from its distaltip and a proximal region extending proximally from the proximal end ofthe distal region. The distal region has a reduced cross-sectional areacompared to the proximal region, with the distal region typicallyincluding only a single lumen and the proximal region including at leasta pair of parallel lumens.

[0015] The lumen in the distal region of the catheter body is contiguouswith both of the parallel lumens in the proximal region. Thus, a driveshaft that is reciprocatably disposed in one of the lumens in theproximal region is able to be selectively advanced to the distal regionor retracted back into the proximal region. The catheter body can beinserted over a guidewire by passing the guidewire through the lumen inthe distal region into the other lumen at the proximal region, i.e., thelumen that is not occupied by the drive shaft. A work element, typicallyan ultrasonic imaging transducer, is mounted at the distal end of thedrive shaft and can be moved in and out of the distal region byreciprocating the drive shaft.

[0016] In use, the catheter body can be introduced over a movableguidewire (or equivalent structure) which has been previously positionedat a desired location within the vascular system. The catheter body ismanipulated until the distal region lies within the location ofinterest, typically a stenotic lesion. Once the catheter body is inposition, the movable guidewire can be retracted (i.e., pulled in theproximal direction) so that it evacuates the lumen in the distal regionbut remains within a lumen in the proximal region. The work element onthe drive shaft, typically an ultrasonic transducer, can then beadvanced in the distal direction so that it enters the lumen in thedistal region. Imaging or another interventional technique may then beperformed using the work element, and, after completion, the workelement may be retracted into its lumen within the proximal region. Theguidewire can then be advanced through the distal region and thecatheter body repositioned over the guidewire so that the distal regionis moved to another location of interest.

[0017] In another aspect, the present invention can provide an improvedcatheter body which can act as a guiding sheath for positioning andrepositioning a variety of working catheters, including ultrasonicimaging catheters, interventional catheters, and the like. Such guidingcatheters comprise a catheter body including a tubular member having aproximal end and a distal end, wherein the tubular member includes aproximal region having at least two lumens and a distal region having asingle lumen which is connected to and in communication with said atleast two proximal lumens. The distal lumen will have a cross-sectionalarea that is less than the combined cross-sectional areas of the twolumens of the proximal region. In this way, the guiding catheter canprovide a low profile at its distal end, while maintaining a guidewireand at least one working catheter within the proximal lumens. In aparticular embodiment, a second working catheter can be introduced overthe movable guidewire in the proximal lumen and selectively through thesingle distal lumen into the blood vessel.

[0018] In an exemplary embodiment, the guiding catheter of the presentinvention includes three proximal lumens, with a guiding catheter in afirst of the proximal lumens, an ultrasonic imaging catheter core in asecond of the proximal lumens, and an interventional catheter, e.g., aballoon angioplasty catheter, in a third of the proximal lumens. Suchguiding catheters can be initially positioned and subsequentlyrepositioned with the guidewire positioned through the single distallumen. While the guidewire is in the single lumen, both the imagingcatheter and the interventional catheter will be retracted within theproximal lumens. After the distal end of the guiding catheter ispositioned within a desired region, typically a stenosed region, theguidewire will be retracted and replaced with either the imaging orinterventional catheters, usually the imaging catheter in order toprovide an initial evaluation of the stenosed region. After imaging thestenosed region, the imaging catheter can be retracted and replaced bythe interventional catheter, e.g., a balloon angioplasty catheter.Usually, the guiding catheter will be retracted sufficiently to exposethe balloon on the balloon catheter to the stenosed region. The stenosedregion can then be treated in a conventional manner, and the balloonangioplasty catheter subsequently retracted back into the proximal lumenof the guiding catheter. The distal end of the guiding catheter can thenbe repositioned within the region of stenosis, the imaging catheter corereturned to the proximal end, and the stenosed region reevaluated byultrasonic imaging. The region can then be retreated, if necessary, orthe guiding catheter can be repositioned to another location using theguidewire in a conventional manner. Optionally, in the three-lumenembodiment, a third working catheter (in addition to the imagingassembly and second working catheter just described) could be introducedover the movable guidewire in the proximal lumen and through the singledistal lumen into the blood vessel.

[0019] Thus, the present invention provides an intravascular catheterwhich combines a distal region having a minimum cross-sectional area tofacilitate entry into coronary arteries and very tight stenotic lesionswith the ability to introduce the catheter over a movable guidewire andretain the guidewire in place during imaging or another interventionalprocedure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020]FIG. 1 illustrates a first catheter of the prior art.

[0021]FIG. 2 illustrates a second, catheter of the prior art.

[0022]FIG. 3 illustrates a catheter constructed in accordance with theprinciples of the present invention.

[0023]FIG. 4 is an enlarged drawing of the distal end of the catheter ofFIG. 3, shown with the work element advanced into the distal region.

[0024]FIG. 5 is a cross-sectional view taken along line 5-5 in FIG. 4.

[0025]FIG. 6 is a cross-sectional view taken along line 6-6 in FIG. 4.

[0026]FIG. 7 illustrates an alternate construction of the catheter ofthe present invention.

[0027]FIG. 8 is a cross-sectional view taken along line 8-8 in FIG. 7.

[0028]FIG. 9 is a cross-sectional view taken along line 9-9 in FIG. 7.

[0029] FIGS. 10-12 illustrate the method of the present invention usingthe catheter of FIGS. 1-6 to image a stenotic lesion.

[0030]FIG. 13 illustrates A second alternate construction of a catheterconstructed in accordance with the principles of the present invention.The catheter of FIG. 13 includes three proximal*lumens for receiving aguidewire, an imaging catheter core, and an interventional catheter,respectively.

[0031]FIG. 14 is a cross-sectional view taken along line 14-14 of FIG.13.

[0032] FIGS. 15-17 illustrate the method of the present invention usingthe catheter of FIGS. 13 and 14 to image and treat a stenotic lesion.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0033] Catheters constructed in accordance with the principles of thepresent invention will comprise an elongate catheter body having aproximal end and a distal end. The catheter body will include at leasttwo regions, with a distal region extending from the distal tip of thecatheter body to a location spaced proximally from the tip and aproximal region extending proximally from the proximal end of the distalregion. The distal region will have a common lumen extendingtherethrough and a reduced cross-sectional area to facilitate entry intocoronary blood vessels and/or tight stenotic lesions. The proximalregion will have a somewhat larger cross-sectional area to accommodateat least two lumens extending therethrough, with a first lumen capableof receiving a conventional movable guidewire and a second lumen capableof receiving a working element attached to the distal end of a driveshaft. Both the first and second lumens connect to the common lumen inthe distal region. Thus, the catheter body may be introduced to a bloodvessel with the guidewire passing through the common lumen at the distalregion and the first lumen in the proximal region. After the catheterbody is in place, the movable guidewire may be retracted within thefirst lumen of the distal region and the working element advanced intothe common lumen from the second lumen in the proximal region. Thecross-sectional area of the distal region is thus minimized since itnever has to simultaneously accommodate both the working element and themovable guidewire.

[0034] A catheter design of the present invention is expected to findits greatest use in the construction of ultrasonic imaging cathetersused for intravascular imaging of blood vessels. In such cases, aworking element will include an ultrasonic transducer having a focallength and operating at a frequency suitable for imaging within thedimensions of a blood vessel. Optionally, the ultrasonic transducer maybe mounted in an assembly together with a reflective member (mirror),where the transducer emits and receives ultrasonic energy in asubstantially axial direction and the mirror is oriented to deflect theemitted and received energy in the radial direction. The use of aconcave mirror to deflect the ultrasonic energy increases the effectivefocal length at which the transducer operates improving image quality.Space between the reflective element and the transducer also eliminates“ring down” effect, thus improving image quality. The design and use ofultrasonic imaging transducers are described in U.S. Pat. Nos.3,938,502; 4,576,177; and 4,794,931; disclosures of which areincorporated herein by reference.

[0035] In addition to ultrasonic transducers, the present invention issuitable for the construction of vascular catheters carrying a varietyof other working elements, particularly rotatable working elements suchas cutters, abraders, rotating mirrors for deflecting laser radiation,and the like. Catheters employing such working elements are described inU.S. Pat. Nos. 4,648,402; 4,669,469; and 4,631,052, the disclosures ofwhich are incorporated herein by reference. The present invention mayfind use whenever the catheter employs a rotatable element that requiresplacement partially or wholly within a catheter sheath in order toprotect blood vessel lining.

[0036] In its broadest aspect, the present invention provides a guidingcatheter and a catheter system capable of introducing a wide variety ofworking catheters, including both ultrasonic imaging catheters andinterventional catheters. Exemplary interventional catheters includeballoon angioplasty catheters, atherectomy catheters, drug perfusioncatheters, laser ablation catheters, mechanical abrasion catheters, andthe like often times, the guiding catheters of the present inventionwill carry two or more working catheters, typically an ultrasonicimaging catheter in combination with an interventional catheter, asillustrated in more detail in FIGS. 13 and 14 hereinafter. It will beappreciated that the guiding catheters and catheter systems of thepresent invention need not employ an imaging catheter, but rather couldemploy only an interventional catheter, or any working catheter otherthan an imaging catheter or imaging catheter core.

[0037] The catheter body (which acts as a guiding catheter) willcomprise one or more flexible tubular members having axial lumens formedtherein, as described in more detail herein below. A catheter body willbe suitable for insertion into and manipulation within a patient'svascular system using techniques which are now well known in the medicalcommunity so that the distal region of the catheter body may be broughtto a desired location within the vascular system.

[0038] The overall dimensions of the catheter will depend on use, withthe length varying widely, typically being between about 40 cm and 150cm, usually being between about 40 cm and 120 cm for peripheralcatheters and being between about 110 cm and 150 cm for coronarycatheters. The diameter of the catheter body may also vary widely, withthe diameter of the distal region typically being between about 2F(French) and 3F, and the diameter of the proximal region typically beingabout 3F and 6F. A particular advantage of the catheter of the presentinvention is that the distal region may be made very small, with thelower limit on size typically being based on the diameter of theultrasonic transducer or other working element which is being achieved.As the size of such working elements is further decreased withadvancements in the art, it is expected that the diameter of thecatheter body of the present invention may be made even smaller.

[0039] The catheter body may be composed of a wide variety ofbiologically compatible materials, typically being made from natural orsynthetic polymers such as silicone rubber, natural rubber,polyvinylchloride, polyurethanes, polyesters, polyethylene,polytetrafluoroethylene (PTFE), and the like. Frequently, the catheterbody may be formed as a composite having a reinforcement materialincorporated within the elastomeric body in order to enhance strength,flexibility, and to toughness. Suitable enforcement layers include wiremesh layers. The flexible tubular members of the catheter body willnormally be formed by extrusion, with one or more integral lumens beingprovided. The catheter diameter can then be modified by heat expansionand shrinkage using conventional techniques. Particular techniques forforming the vascular catheters of the present invention are welldescribed in the patent and medical literature.

[0040] The catheter body may be formed from a single tubular member thatextends the entire distance from the proximal end to the distal end ormay be formed from two or more tubular members that are joined together,either in tandem or in parallel. On the catheter bodies formed from asingle tubular member, the proximal region will be expanded relative tothe distal region and appropriate lumens will be formed in the interiorsof the two regions. Alternatively, the distal region in the catheterbody may be formed from a single tubular member having a single lumenwhile the proximal region is formed from a second tubular member havingat least two axial lumens. The two regions may then be joined togetherso that the common lumen and the distal tubular element is contiguouswith both the parallel axial lumens and the proximal region. As a secondalternative, the catheter body may include a single tubular memberhaving a single axial lumen which extends the entire length from thedistal end to the proximal end. The proximal section is formed bysecuring a second tubular member to the side of the first tubular memberand penetrating the first tubular member so that the respective lumensare made contiguous. The distal region of the catheter is that portionwhich remains forward of the point where the two tubes are joined.

[0041] The distal region of the catheter will typically have a length inthe range from about 1 cm to 20 cm, more typically being in the rangefrom about 2 cm to 10 cm, with the proximal region extending in theproximal direction from the distal region. The proximal region, however,need not extend the entire distance to the proximal end of the catheterbody. It will often be desirable to extend the guidewire lumen formed bythe proximal region only a portion of the distance from the distalregion back toward the proximal end of the catheter body, typicallyextending from about 10 cm to 30 cm, more typically extending from 15 cmto 25 cm. In this way, the guidewire lumen can have a “monorail” designwhich facilitates exchange in the catheter over the guidewire. Suchmonorail designs are described generally in U.S. Pat. No. 4,748,982, thedisclosure of which is incorporated herein by reference.

[0042] The width of the distal region will typically be below about 0.15cm, usually being below about 0.13 cm, and frequently being below about0.1 cm. The width of the proximal region will typically be above about0.17 cm, and frequently being above about 0.2 cm. The width, of course,need not be uniform along the entire catheter length and some variationis permitted.

[0043] The drive shaft which is reciprocatably disposed within a lumenin the proximal region of the catheter will be flexible and suitable fortransmitting torque from the proximal end of the catheter to the workingelement at its distal end. Depending on the application, the drive shaftmay be a solid core wire, but will more typically have a braidedconstruction. Suitable drive shaft constructions are described incopending application Ser. No. 07/500,818, the disclosure of which isincorporated herein by reference. In the case of an ultrasonictransducer as the working element, the drive shaft will also carry thenecessary electrical leads for connecting the transducer.

[0044] Catheters according to the present invention will include ahousing formed at the proximal end of the catheter body. The housingwill seal the interior lumen of the catheter body which carries thedrive shaft and will provide means for reciprocating the drive shaftaxially within the catheter body. In the case of ultrasonic imagingcatheters, the housing will also include the necessary electricalconnection means for coupling the electrical leads on the drive shaft tothe associated electronic imaging producing equipment. The drive shaftwill further include a spindle or other means for coupling the driveshaft to an electric drive motor for rotating the ultrasonic transduceror other working element. Suitable spindles and drive motors areillustrated in U.S. Pat. No. 4,771,774, the disclosure of which isincorporated herein by reference.

[0045] Referring now to FIG. 3, a first embodiment 50 of the catheter ofthe present invention is illustrated. The catheter 50 includes aflexible catheter body 52 having a distal region 54 and a proximalregion 56. The distal region 54 includes a single lumen 58 which extendsfrom a distal port 60 to a transition region 62. The proximal region 56includes a first lumen 64 and second lumen 66. The first lumen 64carries a movable guidewire 68 which, as illustrated, extends from aproximal port 70 through the lumen 58 and in distal region 54 and outthe distal port 60. In this way, a catheter 50 can be inserted over theguidewire 68 in a conventional manner.

[0046] Drive shaft 72 is reciprocatably disposed within the second lumen66. As illustrated in FIG. 3, ultrasonic imaging assembly 74 is securedto the distal end of the drive shaft 72 and remains within the proximalregion 56 when the guidewire 68 extends into lumen 58 of the distalregion 54. As illustrated in FIG. 4, however, once the guidewire 68 isretracted into the first lumen 64, the ultrasonic imaging assembly 74may be advanced axially forward into the lumen 58 of the distal region54.

[0047] In the preferred embodiment, the ultrasonic imaging assembly 74includes an ultrasonic transducer 76 (FIG. 4) which is oriented to emitultrasonic energy in the axially forward direction, and a mirror 78which is disposed to deflect the ultrasonic energy from transducer 76 ina generally radial direction. The ultrasonic transducer 76 and mirror 78are fixedly mounted relative to each other within the assembly 74 sothat they will rotate together as the drive shaft 72 is rotated.

[0048] Catheter 50 further includes a proximal housing 80 secured to theproximal end of the catheter body 52. Proximal housing 80 includes alever 82 which is attached to the drive shaft 72 which permits the userto selectively reciprocate the ultrasonic imaging assembly 74 betweenits retracted position (as illustrated in FIG. 3) and its extendedposition (illustrated in FIG. 4.) The ultrasonic imaging assembly 74would normally be utilized only when it is in its extendedconfiguration. It will be retracted when the catheter 50 is beingpositioned over the movable guidewire 68.

[0049] The housing 80 further includes an electrical connector plug 84for coupling the electrical leads on the drive shaft 72 to the necessaryelectrical instrumentation for producing the ultrasonic image and aspindle 86 at the proximal terminal end of the drive shaft 72 forcoupling to a motor drive, as described hereinabove. Conveniently ringsand commutators (not shown) may be provided in a conventionalarrangement to couple electrical leads (not shown) from the transducer76 (running along or through the drive shaft 72) to the connector plug84.

[0050] Referring now to FIGS. 7-9, an alternate embodiment 100 of thecatheter of the present invention is illustrated. The catheter 100includes a first flexible tubular member 102 that extends from a distalend 104 to a proximal end (not illustrated) of the catheter body. Thefirst flexible tubular element defines a single lumen 106 that extendsthe entire length of the catheter body and terminates in a distal port108. A proximal region 110 of the catheter 100 is defined by a secondflexible tubular member 112 which is attached to the side of the firstflexible tubular member 102 and which is interconnected with the lumen106 of the first flexible tubular member through a port 114. A distalregion 120 of the catheter 100 as defined as that region of the firstflexible tubular member 102 which lies distally of the connecting port114. Lumen 122 of the second flexible tubular member 112 is suitable forreceiving a guidewire 130 in a conventional “monorail” fashion, whilethe lumen 106 of the first flexible tubular member 102 receives a driveshaft 132 having an ultrasonic imaging assembly 134 at its distal end.As illustrated in FIG. 7, the ultrasonic imaging assembly 134 lieswithin the distal region 120 of the catheter 100. The imaging assembly134, of course, could be retracted to within the proximal region. 110 ofthe catheter behind port 114. This way, the lumen 106 of the distalregion 120 would be free to receive the advance of the guidewire 130 forpositioning or repositioning of the catheter 100.

[0051] Referring now to FIGS. 10-12, use of the catheter 50 andguidewire 68 of FIG. 3 in positioning the catheter within a region ofstenosis S within a blood vessel BV will be described. Initially, theguidewire 68 is introduced to the blood vessel in the conventionalmanner so that the distal end lies beyond the region of stenosis, asillustrated in FIG. 10. After positioning of the guidewire 68, thecatheter 50 is introduced over the guidewire by passing the proximal endof the guidewire 60 through distal port 60 and subsequently threadingthe guidewire through lumen 58 on the distal region 54 and lumen 64 inthe proximal region 56. The catheter is advanced axially forward withinthe blood vessel until the proximal region 54 lies within the region ofstenosis. After the catheter 50 has been properly positioned, theultrasonic imaging assembly 74 may be advanced to the position shown inFIG. 11 (or alternatively it may have been in such position while thecatheter was being introduced to the blood vessel). After the imagingassembly 74 is located near the distal end of lumen 66, the guidewire 68will be retracted in the distal direction until it is removed from lumen58 in the distal region and lies wholly within lumen 64 within theproximal region 56. Once lumen 58 is cleared of a guidewire 68, theultrasonic imaging assembly 74 may be advanced axially forward into thelumen 58, where it can then be used for imaging in a conventionalmanner.

[0052] At any time during the imaging procedure, the drive shaft 72 canbe retracted to once again clear lumen 58. After clearing the lumen, theguidewire can again be advanced axially forward so that it is availablefor repositioning the catheter 50. Alternatively, the guidewire 68 maybe left in place and the catheter 50 withdrawn over the guidewire sothat it remains in place for different catheters to be introduced.

[0053] Referring now to FIGS. 13 and 14, a second alternate embodiment200 of a catheter system constructed in accordance with the principlesof the present invention is illustrated. The catheter system 200includes a first flexible tubular member 202 that defines a guidingcatheter for both an ultrasonic imaging assembly 204 and a balloonangioplasty catheter 206. The tubular member 202 extends from a distalend 208 to a proximal end 210, defining a single lumen 212 over a distalregion thereof. A portion of flexible tube 202 that lies proximal to thesingle lumen 212 includes three separate lumens 214, 216, and 218, asbest illustrated in FIG. 14. The balloon angioplasty catheter 206 isreciprocatably received in first lumen 214, while a movable guidewire220 is received in the second lumen 216, and the ultrasonic imagingassembly 204 is received in the third lumen 218. The ultrasonic imagingassembly 204 is attached to a drive and reciprocation assembly 230,which is similar to the assembly illustrated in FIG. 3 described above.A proximal end of the balloon angioplasty catheter 206 and a proximalend of the guidewire 220 pass out through side ports formed along thelength of the flexible tubular member 202. As illustrated, the lumens214 and 216 that receive the angioplasty catheter 206 and guidewire 220,respectively, both extend substantially the entire length of the tubularmember 202 and terminate near the proximal end 210 thereof. The presentinvention, however, contemplates that the guidewire and other workingcatheter lumens may terminate much nearer the distal end of the tubularmember 202, to provide for “monorail” catheter designs as describedpreviously.

[0054] Referring now to FIGS. 15-17, use of the guiding catheterassembly 200 for imaging and treatment of a stenotic region S within ablood vessel BV will be described. The initial positioning and imagingsteps will be performed substantially as set forth in the description ofFIGS. 10-12, above. After the stenotic region S has been initiallyimaged, the imaging assembly 204 will be withdrawn into the proximallumen 218 of the guiding catheter body 202, and the guiding catheterbody partially withdrawn so that the distal region of the catheter ispulled out from the stenotic region. The balloon end of catheter 206will then be advanced into the stenotic region S (optionally employing afixed guidewire 207 at its distal tip). In some cases, it may bedesirable to initially position the balloon end of catheter 206 withinthe lumen 212 of the guiding catheter and to thereafter draw the distalend of the catheter from over the balloon, resulting in positioning ofthe balloon within the stenotic region.

[0055] In either case, the balloon catheter 206 will be positionedwithin the stenotic region S, as illustrated in FIG. 15. The balloon maythen be inflated, as illustrated in FIG. 16, in a conventional manner inorder to dilate the stenosed region S. After deflating the balloon, thecatheter 206 may then be withdrawn to within the proximal lumen 214. Thedistal end of tubular member 202 may then be advanced back into thetreated stenosed region S, as illustrated in FIG. 17. Optionally, theguidewire 220 could first be advanced into the stenosed region S and thetubular member 202 then repositioned over the guidewire. In either case,the treated stenosed region S can then be imaged using the ultrasonicimaging assembly 204, by advancing the assembly into the distal regionof the tubular member 202 of the catheter. The treated stenosed region Scan thus be assessed, and it can be determined whether additionalballoon angioplasty or other treatment modalities are indicated.

[0056] Although the foregoing invention has been described in detail forpurposes of clarity of understanding, it will be obvious that certainmodifications may be practiced within the scope of the appended claims.

What is claimed is:
 1. A method of performing an intravascular procedurein a patient using an introducer sheath having first and second lumens,a distal end of the second lumen terminating and communicating with thefirst lumen at a location proximal of a distal opening of the firstlumen, comprising the steps of: placing a first intravascular device inthe first lumen of the introducer sheath so that the distal end of theintravascular device is proximal the location where the second lumencommunicates with the first lumen; placing a second intravascular devicein the second lumen of the introducer sheath so that the distal end ofthe intravascular device is proximal the location where the second lumencommunicates with the first lumen; positioning the introducer sheath ina distal region of the patient's vasculature so that at least a portionof both lumens are in the vasculature; and advancing the first secondintravascular device past the location where the second lumencommunicates with the first lumen.
 2. The method of claim 1 furthercomprising the step of extending the first intravascular device throughthe first lumen past the distal end of the introducer sheath into thevessel of the patient.
 3. The method of claim 2 further comprising thestep of withdrawing the first intravascular device into the introducersheath to a point proximal the location where the second lumencommunicates with the first lumen.
 4. The method of claim 3 furthercomprising the step of advancing the second intravascular device pastthe location where the second lumen communicates with the first lumenand into the first lumen.
 5. The method of claim 4 further comprisingthe step of extending the second intravascular device through the firstlumen past the distal end of the introducer sheath into the vessel ofthe patient.
 6. The method of claim 5 further comprising the step ofwithdrawing the second intravascular device into the introducer sheathto a point proximal the location where the second lumen communicateswith the first lumen.
 7. The method of claim 6 further comprising thestep of withdrawing the introducer from the patient's vasculature. 8.The method of claim 7 further comprising the step of withdrawing thesecond intravascular device into the introducer sheath to a pointproximal the location where the second lumen communicates with the firstlumen.
 9. The method of claim 8 further comprising the step ofwithdrawing the introducer sheath from the patient's vasculature. 10.The method of claim 1 in which the first intravascular device is a guidewire, the advancing step further comprising:
 11. An intravascularintroducer for use in conjunction with a guide catheter for positioningother intravascular devices into the coronary vasculature, theintroducer comprising: an elongate tubular member having a proximal endand a distal end sized to be located inside of the guide catheter, theelongate member having: a first lumen extending from the proximal end ofthe elongate member to the distal end of the elongate member; a firstopening located at the proximal end of the elongate member, the firstopening communicating with the first lumen; a second opening located atthe distal end of the elongate member, the second opening communicatingwith the first lumen; a second lumen extending adjacent to the firstlumen along at least a portion of the elongate member, the second lumencommunicating with and merging into the first lumen at a locationproximal of the second opening; and a third opening communicating with aproximal end of the second lumen, whereby a first intravascular devicecan be removably positioned in the first lumen, a second intravasculardevice can be removably positioned in the second lumen, and the firstand second intravascular devices can be alternatively advanced past thelocation at which the first and second lumens merge, the first andsecond lumen separated by at least one wall that joins the lumens at thethird opening.
 12. The introducer of claim 11 in which the third openingis located at the proximal end of the elongate member.
 13. Theintroducer of claim 11 in which the third opening is located distally ofthe proximal end of the elongate member.
 14. The introducer of claim 11in which the first and second lumens permit the complete withdrawal ofany intravascular devices located therein.
 15. An intravascularintroducer for positioning other intravascular devices into a person'svasculature, the introducer comprising: an elongate tubular memberhaving: a distal section having a single lumen communicating with adistal opening; and a proximal section configured for insertion into theperson's vasculature, the proximal section having two lumens, the twolumens merging into the single lumen, and further the proximal sectionhaving a first proximal opening communicating with one of the two lumensand a second proximal opening located proximal of the merging regionsand communicating with the other of the two lumens, wherein the firstand second lumens are separated by at least one wall that joins thelumens at the proximal openings.
 16. The introducer of 15 in which theproximal section comprises: a proximal part and a distal part, andfurther in which the first proximal opening is located at a proximal endof the proximal part, and the second proximal opening is located at aproximal end of the distal part.